A droplet actuator typically includes one or more substrates configured to form a surface or gap for conducting droplet operations. The one or more substrates establish a droplet operations surface or gap for conducting droplet operations and may also include electrodes arranged to conduct the droplet operations. The droplet operations substrate or the gap between the substrates may be coated or filled with a filler fluid that is immiscible with the liquid that forms the droplets. Bubble formation in the filler fluid in a droplet actuator can interfere with functionality of the droplet actuator. There is a need for techniques for preventing unwanted bubbles from forming in the filler fluid in a droplet actuator.